Author Topic: BSA A7 oil leaks  (Read 843 times)

Offline tim

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BSA A7 oil leaks
« on: 21.05. 2018 11:27 »
Hello forum members!
Anyone know why oil leaks out from behind/ above the oil pump on my A7?

Offline muskrat

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Re: BSA A7 oil leaks
« Reply #1 on: 21.05. 2018 13:21 »
G'day Tim,  *welcome*.
Do you mean with or without the cover on?
If cover on and not a gasket leak it could be coming from where the dynamo meets the inner cover. But only if the dynamo drive compartment is full of oil which it should not.
If cover off (and motor not running) it would be coming out the main bush, which means the anti siphon ball/valve is leaking.
Cheers
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Offline tim

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Re: BSA A7 oil leaks
« Reply #2 on: 21.05. 2018 13:25 »
Thanks for prompt reply. Oil pours out from behind/above oil pump when started with the timing cover off. Oil is not returning to tank.

Offline muskrat

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Re: BSA A7 oil leaks
« Reply #3 on: 21.05. 2018 14:00 »
With the cover ON does the oil return to the tank?
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Online orabanda

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Re: BSA A7 oil leaks
« Reply #4 on: 21.05. 2018 15:29 »
The oil is leaking between the timing bush & journal.

Offline tim

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Re: BSA A7 oil leaks
« Reply #5 on: 21.05. 2018 20:38 »
No the oil used to return but not now.

Offline tim

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Re: BSA A7 oil leaks
« Reply #6 on: 21.05. 2018 20:45 »
Hoping for an easy solution to this but fear the worst! Does the engine need splitting or is there any other way? Would compressed air clear this?
Thanks

Offline muskrat

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Re: BSA A7 oil leaks
« Reply #7 on: 21.05. 2018 21:15 »
G'day Tim.
OK we need a little background. What has been touched since the last time it was all good? Is this after a long lay up? Has the pump been off and a new gasket is covering a port?
The ball in the scavenge pipe may be stuck. Drop the sump plate and poke it, I'd give it a squirt of carb clean. Then check for blockages on the return to the tank.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Muskys Plunger A7

Offline tim

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Re: BSA A7 oil leaks
« Reply #8 on: 21.05. 2018 21:40 »
Hello Muskrat
Yes lots of work done to bike since it was working well. I only noticed the oil leak after fitting a reconditioned dynamo after the winter lay up. I have fitted a new oil pump gasket. I drained oil and checked scavenger valve also. I really do not want to split the engine - the sun is shining here in the UK and I would love to be out enjoying it all on the A7.

Offline muskrat

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Re: BSA A7 oil leaks
« Reply #9 on: 21.05. 2018 21:54 »
Did you have the oil pump apart? The gasket may be scewif and blocking a port. 1st thing I'd check, then other blockages.
Cheers
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Re: BSA A7 oil leaks
« Reply #10 on: 21.05. 2018 23:34 »
 His Tim  I was thinking blockages in the return line too.... what model A7 is it?
 Disconnect the return line at the engine end and blow air through the hose from the tank return (top of rocker feed first), and then crank the engine over to see if oil comes out the spigot.
 Apparently some have had issues with new gaskets where some of the important holes were partly obscured by the gasket, so check that if you didn't already


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Re: BSA A7 oil leaks
« Reply #11 on: 22.05. 2018 00:04 »
Put some safety glasses on, and an old shirt.
Take off the oil pump, and blow air into the oil passage (hole) in the crankcase (where the oil pump sits) that delivers oil to the timing bearing (note that the anti- wet sumping check valve is behind this port).
Air (and oil) is likely to blow out at you, from between the crankshaft journal and the bore of the timing bush. Often it will also blow out from between the outside diameter of the bush, and the crankcase housing, as the bore in the casing usually elongates with time (rpm, lots of miles on the road).

If any air comes out (at you) then so will the oil when the engine isn't running, because the anti-siphon valve is not 100% reliable - the spring is very light, and long, and the ball seats in the alloy crankcase (prone to damage on the counter bore where the ball seats).

This is an easy way for you to gauge if the clearances are too great; if you emerge looking like a 50's rocker with bryllcream in your hair, then there is too much clearance - speaking from experience!

In summary, heavy wet sumping can be caused by:

Excessive wear on the timing side crankcase journal
Ditto for the timing bush bore
the bore in the crankcase half (for the timing bush) out of round; often between 0.010"- 0.014". If this is the case the housing should be bored until the bore cleans up (is concentric) and an oversize bush made with 0.0015"= 0.002" interference fit.
Worn oil pump
Oil pump not sitting flat on the gasket

Richard



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Re: BSA A7 oil leaks
« Reply #12 on: 22.05. 2018 08:18 »
Hello Muskrat
Yes lots of work done to bike since it was working well. I only noticed the oil leak after fitting a reconditioned dynamo after the winter lay up. I have fitted a new oil pump gasket. I drained oil and checked scavenger valve also. I really do not want to split the engine - the sun is shining here in the UK and I would love to be out enjoying it all on the A7.

Probably not related to your leak problem but a common mistake is to omit a fibre washer under the end bolt of the pump body, which makes up for their not being a gasket between the body and case there.

This can lead to a distorted pump body if one should have been fitted, and wasn’t.

Edit, see:  https://www.draganfly.co.uk/index.php/accessories-a-misc/product/14028-
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Offline tim

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Re: BSA A7 oil leaks
« Reply #13 on: 22.05. 2018 17:01 »
Oil still pouring out above oil pump. Decided to put timing cover back on to see what happens and yes oil now returning to tank!

Offline muskrat

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Re: BSA A7 oil leaks
« Reply #14 on: 22.05. 2018 21:06 »
G'day Tim.
OK I've put up a pic of a timing side. Red horizontal arrow points to a hole in the cases, oil will escape from there as the crank is whizzing round flinging all the oil that is pumped into the crank. That's normal. The yellow arrow is pointing to the crank journal and bush joint (behind the pimion), a little oil will escape from there. The red virtical arrow points to the case and bush joint, no oil should leak from there (see Orabandas post).
 If the sump and oil lines have been drained it will take quite some time (a minute or so) for oil to be returned to the tank, which can worry the uninitiated.
Cheers

PS: Now get over to the Introductions section and tell us all about your love for A7's
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7